Method for transmitting an uplink signal and feedback information, and relay apparatus using the method

ABSTRACT

The invention relates to a method for transmitting an uplink signal and feedback information of a relay, and to a relay apparatus using the method. The relay can receive information, constituting a downlink backhaul subframe and an uplink backhaul subframe from a base station. The relay can transmit an uplink signal via the relevant uplink backhaul subframe on the basis of the received information constituting the uplink backhaul frame. Further, the relay can receive a downlink reference signal from the base station, measure the status of a channel, and transmit the status of the channel in values, in various formats and in various points in time and cycles, to the base station.

TECHNICAL FIELD

The present invention relates to an uplink signal and feedbackinformation transmitting method.

BACKGROUND ART

In a link between a base station and a user equipment according to arelated art, channel variation is serious due to mobility of the userequipment. Therefore, in case of downlink, a user equipment performs achannel measurement using a reference signal (RS) received from a basestation and is then able to feed back a result of the channelmeasurement in form of a channel quality index (CQI), a precoding matrixindex and the like. If so, the base station is able to perform a linkadaptation for a downlink transmission to from the base station to theuser equipment based on the feedback information. Since a channel statusmay vary seriously in accordance with time due to mobility of the userequipment, the user equipment is able to transmit CQI, PMI and the likeby performing the channel measurements periodically.

In case of uplink, a base station is able to measure an uplink channelstatus based on a sounding reference signal (SRS) received from a userequipment. And, a link adaptation for an uplink transmission can beperformed through this channel status measurement. For this, the basestation is able to periodically allocate sounding reference signals to aplurality of user equipments.

In case that a channel status between a base station and a userequipment is poor, it is able to provide a radio channel having a betterchannel status to the user equipment by installing a relay node betweenthe base station and the user equipment. If a relay node is introducedon a cell boundary area having a poor channel status from a basestation, a faster data channel can be provided and a cell service areacan be extended. Thus, the relay node is the technology introduced toget rid of a radio wave shade area in a wireless communication systemand is being used widely. A recent relay node scheme continues to bedeveloped into a further intelligent form, whereas a past relay nodescheme if limited to a repeater function of amplifying and transmittinga signal simply. Moreover, the relay node technology corresponds to thetechnology mandatory for the service coverage extension and the datathroughput improvement by reducing the cost for the base stationestablishment and the maintenance expense for a backhaul network in thenext generation mobile communication system. In accordance with theongoing development of the relay node technology, a new wirelesscommunication system needs to support a relay node used by a related artwireless communication system.

In LTE-A system, a link between a base station and a relay node is ableto use a backhaul link, while a link between a base station and a userequipment is able to use an access link. Since a relay node plays a rolein relaying data, signals and the like received from a base station to auser equipment, a subordinate relay and the like, it can exist in astationary form that barely has mobility. In case of considering ascenario for arranging a relay node existing in a stationary form, itcan be said that a relay node almost has no variation of a channelstatus in accordance of elapse of time. In particular, the relay node ischaracterized in that a channel status for a specific frequency band isalmost time-invariant.

A relay node, of which channel status is less variant in accordance withtime on a specific frequency band, may not need to make a channelmeasurement report, i.e., a CQI/PMI (channel quality index/precodingmatrix index) feedback, repeatedly with a predetermined cycle like theconventional user equipment and base station. This may cause a problemof increasing a resource overhead or a problem of degradingcommunication performance. Yet, any effort has not been made to researchand develop a detailed method for a relay node to feed back a channelstatus to a base station until now.

A relay node plays a role in delivering data received from a basestation to a user equipment within an area and also plays a role indelivering data received from a user equipment belonging to its area toa base station. Yet, since it is not preferable that the relay nodereceives data, signals and the like from the base station as soon astransmits data to the user equipments, a subframe capable of signaltransmission and reception may be limited. Therefore, many efforts needto be made to research and develop a method of allocating backhaulsubframes capable of communication between a base station and a relaynode and a corresponding signaling method. When an allocationinformation on an uplink backhaul subframe and a corresponding signalingare not defined in a relay node, if the relay node receives data from abase station and a user equipment simultaneously, it causes a problemthat error occurs in the data.

DISCLOSURE OF THE INVENTION Technical Problem

An object of the present invention is to provide a method oftransmitting an uplink signal of a relay node.

Another object of the present invention is to provide a method oftransmitting feedback information of a relay node.

Another object of the present invention is to provide a relay apparatusfor transmitting an uplink signal.

A further object of the present invention is to provide a relayapparatus for transmitting feedback information.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims thereof as well as the appended drawings.

Technical Solution

To further achieve these and other advantages and in accordance with thepurpose of the present invention, an uplink signal transmitting methodof a relay node according to the present invention includes the steps ofreceiving a downlink (DL) backhaul subframe including a uplink (UL)grant information from a base station and transmitting a signal to thebase station via a specific UL backhaul subframe based on the receivedUL grant information, wherein the UL grant information includes a timingindication information and wherein the timing indication informationcomprises an information about an interval from a DL backhaul subframecorresponding to the received UL grant information to the UL backhaulsubframe transmittable in UL by the relay node.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, a method of transmitting an uplinksignal in a relay node according to the present invention includes thesteps of receiving a downlink (DL) backhaul subframe pattern informationfrom a base station and transmitting the uplink signal to the basestation via a uplink (UL) backhaul subframe based on an intervalinformation indicating from a DL backhaul subframe to the UL backhaulsubframe, wherein the DL backhaul subframe pattern information includesan index information of the DL backhaul subframe and wherein theinterval information comprises a predetermined value or is signaled fromthe base station.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, a method of transmitting feedbackinformation at a relay node according to the present invention includesthe steps of receiving a downlink (DL) reference signal from a basestation, measuring a channel status using the received DL referencesignal, and transmitting a differential value between the measuredchannel status value and a reference value, the measured channel statusvalue whenif the differential value is grater than a preset thresholdvalue or a differential value between the measured channel status valueand a last reported channel status value to the base station as thefeedback information.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, a method of transmitting feedbackinformation at a relay node according to the present invention includesthe steps of receiving a downlink (DL) reference signal from a basestation, measuring a channel status using the received DL referencesignal, and if a differential value between the measured channel statusvalue and a last reported channel status value is equal to or greaterthan a threshold value, transmitting the measured channel status valueor the differential value as the feedback information to the basestation.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, a relay node apparatus fortransmitting an uplink signal according to the present inventionincludes a receiving unit for receiving a downlink (DL) backhaulsubframe containing a uplink (UL) grant information from a base stationand a transmitting unit for transmitting a signal to the base stationvia a specific UL backhaul subframe based on the received UL grantinformation, wherein the UL grant information includes a timingindication information and wherein the timing indication informationcomprises an information corresponding to an interval from a DL backhaulsubframe corresponding to the received UL grant information to the ULbackhaul subframe transmittable in UL by the relay apparatus.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, a relay apparatus for transmitting afeedback information according to the present invention includes areceiving unit for receiving a DL reference signal from a base station,a channel status measuring unit for measuring a channel status using thereceived DL reference signal, and a transmitting unit for transmitting adifferential value between the measured channel status value and areference value, the measured channel status value (if the differentialvalue is grater than a preset threshold value) or a differential valuebetween the measured channel status value and a last reported channelstatus value to the base station as the feedback information.

ADVANTAGEOUS EFFECTS

Accordingly, an uplink signal transmitting method of a relay nodeaccording to the present invention is able to efficiently transmit anuplink signal to a base station by keeping pace with a timing for anuplink backhaul subframe.

Moreover, a feedback information transmitting method of a relay nodeaccording to the present invention is able to considerably reduce aresource overhead due to frequent feedbacks and is also able to enhancecommunication performance of the relay node.

Effects obtainable from the present invention are non-limited the abovementioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a diagram for a configuration of a relay backhaul link and arelay access link in a wireless communication system.

FIG. 2 is a schematic diagram of a frame structure in 3GPP LTE systemfor example of a mobile communication system.

FIG. 3 is a diagram for one example of a frame structure used for a DLtransmission by a base station and a relay node.

FIG. 4 is a diagram for one example of a frame structure used by a basestation in a wireless communication system using a relay node.

FIG. 5 is a diagram for a configuration of a relay node apparatusaccording to a preferred embodiment of the present invention.

BEST MODE FOR INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. In the following detailed description of the inventionincludes details to help the full understanding of the presentinvention. Yet, it is apparent to those skilled in the art that thepresent invention can be implemented without these details. Forinstance, although the following descriptions are made in detail on theassumption that a mobile communication system includes 3GPP LTE (3^(rd)generation partnership project long term evolution) system, they areapplicable to other random mobile communication systems except uniquefeatures of 3GPP LTE.

Occasionally, to prevent the present invention from getting vaguer,structures and/or devices known to the public are skipped or can berepresented as block diagrams centering on the core functions of thestructures and/or devices. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

Besides, in the following description, assume that a terminal is acommon name of such a mobile or fixed user stage device as a userequipment (UE), a mobile station (MS), an advanced mobile station (AMS)and the like. And, assume that that a base station is a common name ofsuch a random node of a network stage communicating with a terminal as anode B, eNode B, a base station, an access point (AP) and the like.Moreover, a relay can be called a relay node (RN), a relay station (RS)or the like.

In a mobile communication system, a user equipment can receiveinformation in downlink from a base station. The user equipment is alsoable to transmit information in uplink. The informationtransmitted/received by the user equipment includes data and variouskinds of control information. And, various physical channels existaccording to types and usages of the information transmitted or receivedby the user equipment.

FIG. 1 is a diagram for a configuration of a relay backhaul link and arelay access link in a wireless communication system.

Referring to FIG. 1, a relay node (RN) is able to receive informationfrom a base station in a relay backhaul downlink and is also able totransmit information to the base station in a relay backhaul uplink.Moreover, the relay node is able to transmit information to a userequipment in a relay access downlink and is also able to receiveinformation from the user equipment in a relay access uplink.

The relay node is able to perform an initial cell search job such as asynchronization match with the base station and the like. For this, therelay node receives a synchronization channel from the base station,matches synchronization with the base station, and is able to obtainsuch information as cell ID and the like. Thereafter, the relay nodereceives a physical broadcast channel from the base station and is thenable to obtain intra-cell broadcast information. Meanwhile, the relaynode receives a downlink reference signal in the initial cell searchstep and is then able to check a channel status of the relay backhauldownlink. The relay node receives a physical downlink control channel(R-PDCCH: relay-physical downlink control channel) and a physicaldownlink control channel (R-PDSCH: relay-physical downlink controlchannel) in accordance with the physical downlink control channelinformation and is then able to obtain a detailed system information.

Meanwhile, if the base station is initially accessed or there is noradio resource for signal transmission, the relay node is able toperform a random access procedure on the base station. For this, therelay node transmits a specific sequence as a preamble on a physicalrandom access channel (PRACH) or the like and is then able to receive aresponse message for the random access on a relay physical downlinkcontrol channel and a corresponding relay physical downlink sharedchannel. In case of a contention based random access except a case ofhandover, the relay node is then able to perform such a contentionresolution procedure as a transmission of an additional physical randomaccess channel and R-PDCCH/R-PDSCH reception.

Having performed the above-described procedures, the relay node is ableto perform an R-PDCCH/R-PDSCH and R-PUSCH/R-PUCCH (relay-physical uplinkshared channel/relay-physical uplink control channel) transmission as ageneral uplink/downlink signal transmission procedure. In this case, thecontrol information, which is transmitted to the base station in uplinkby the relay node or received by the base station from the relay node,can include a DL/UL (downlink/uplink) ACK/NACK signal, a channel qualityinformation (channel quality indicator: CQI), a precoding matrix index(PMI), a rank indicator (RI) and the like. In case of the 3GPP LTE(3^(rd) generation partnership long term evolution) system, the relaynode is able to transmit such control information as CQI, PRI, RI andthe like on R-PUSCH/R-PUCCH.

FIG. 2 is a schematic diagram of a frame structure in 3GPP LTE systemfor example of a mobile communication system.

Referring to FIG. 2, a single radio frame can include 10 subframes. And,a single subframe is able to include 2 slots in time domain. A timetaken to transmit a single subframe can be defined as a transmissiontime interval (TTI). For instance, a single subframe has a length of 1ms and a single slot can have a length of 0.5 ms. Moreover, a singleslot is able to include a plurality of OFDM (orthogonal frequencydivision multiplexing) symbols in time domain.

In 3GPP LTE system, OFDMA scheme is used in downlink and OFDM symbol isable to indicate a symbol cycle. And, the OFDM symbol can be regarded asone SC-FDMA symbol or one symbol cycle. A resource block (RB) is aresource allocation unit and is able to include a plurality ofsubcarriers adjacent to one slot. For instance, 10 subframes areincluded in a single radio frame, 2 slots are included in a singlesubframe, and 14 OFDM symbols are included in a single slot. Yet, eachof the number of subframes, the number of slots and the number of OFDMsymbols can be changed into one of various values.

In the following description, various methods of configuring uplink(hereinafter abbreviated UL) backhaul subframes, via which a basestation will receive signals, data, information and the like from arelay node, are explained.

First of all, backhaul transmitting/receiving between a base station anda relay node can be possible only in a backhaul subframe allocated by adonor base station (or a donor eNB). The donor base station sets apattern for the backhaul subframe by setting a cycle to one of 10 ms, 40ms and the like and is then able to inform the relay node of thesetting.

According to one embodiment of the present invention, when a basestation configures an uplink backhaul subframe, the base station is ableto allocate a downlink (hereinafter abbreviated DL) backhaul subframe.If so, the base station is able to allocate the UL backhaul subframebased on a pattern of the allocated DL backhaul subframe. For instance,a base station is able to allocate a subframe, which is spaced apartfrom a corresponding DL backhaul subframe number by a prescribed number(N) of subframe(s), as a UL backhaul subframe. In this case, the N canbe implicitly fixed to a given DL subframe pattern. In particular, thevalue N is the predetermined value and a relay node may be already awareof the value N. Specifically, the value N can be set to one of 4, 5 and6. For instance, assuming N=4, a base station is able to allocate asubframe, which is spaced apart from a corresponding DL backhaulsubframe number by 4 subframes, as a UL backhaul subframe.Alternatively, a base station is able to explicitly signal a UL backhaulsubframe to a relay node together with a DL backhaul subframe pattern.By such a method, the relay node can be aware of the subframe to whichthe UL backhaul subframe is allocated.

According to one embodiment of the present invention, when a basestation configures an uplink backhaul subframe, the base station is ableto set a DL backhaul subframe pattern to such a cycle as 10 ms, 40 msand the like. And, the base station is able to set a UL backhaulsubframe pattern to the same cycle of the DL subframe pattern.

For instance, in case that a base station sets a DL backhaul subframepattern to a cycle of 10 ms, the bas station is able to allocate 6subframes (i.e., indexes 1, 2, 3, 6, 7 and 8) except the subframes ofwhich subframe indexes are 0, 4, 5 and 9 to the DL backhaul subframes,respectively. In this case, it is able to allocate the DL backhaulsubframes in a manner of explicitly signaling 6 bitmaps in bitmap formatfor the 6 subframes that can be allocated as the DL backhaul subframes.

Moreover, for the UL backhaul subframe allocation, the base station setsa UL backhaul subframe allocation pattern to a cycle of 10 ms or 40 msin the same manner of the DL backhaul subframe and is then able toexplicitly signal the allocation to a relay node. In doing so, the basestation signals the UL backhaul subframe pattern in the bitmap format tothe relay node using 10 or 40 bitmaps according to the pattern cycle of10 ms or 40 ms. In particular, in case that the base station allocatesthe UL backhaul subframe pattern with the cycle of 10 ms, the basestation is able to explicitly signal the UL backhaul subframe pattern as10 bitmaps for 10 subframes set to the subframe indexes 0 to 9 to therelay node. By this method, the relay node can be aware of the subframeto which the UL backhaul subframe is allocated.

A base station is able to allocate a UL backhaul subframe by a grantbased scheme.

According to one embodiment of the present invention, when a basestation configures an uplink backhaul subframe, the base station is ableto signal a UL backhaul subframe to a relay node via a UL grant of a DLbackhaul subframe. The DL backhaul subframe including the UL grant cancontain resource allocation information on the UL backhaul subframeindicated by the corresponding UL grant.

Information on a timing indication may be included in a UL grant field.And, the base station is able to transmit the UL grant including thetiming indication information to the relay node. In this case, thetiming indication information is situated within the UL grant field andis able to indicate a position at which the UL backhaul subframe isallocated. In particular, the timing indication information indicatesthat a UL backhaul subframe is allocated to a subframe spaced apart fromDL backhaul subframes including the corresponding UL grant by aprescribed number (N) of subframes. In this case, the ‘N’ is a value inconsideration of a processing time of a relay node, an ACK/NACK feedbacktiming for a DL backhaul transmission and the like. In accordance withthe limitation put on the N value, the base station is able to determinethe bit number to signal to N value to the relay node. In this case, theN value is not a fixed value but can vary dynamically. For instance, ifN is a natural number on the condition of 4≦N≦6, the base station isable to signal the N value using 2 bits. By this method, the relay nodecan be aware of the subframe to which the UL backhaul subframe isallocated.

In the following description, another application scheme of the schemeof enabling the timing indication information to be included in the ULgrant information is explained. First of all, when a base stationconfigures a UL backhaul subframe through an explicit signaling of thebitmap scheme, the scheme can be applied in a manner of indicating a ULbackhaul subframe on which a resource allocation for a UL transmissionis performed through a corresponding UL grant field among the set ULbackhaul subframes.

For instance, for a specific relay node, a base station is able toallocate each DL subframe #1 (e.g., subframe index 1) in a cycle of aradio frame of 10 ms to a DL backhaul subframe through an explicitsignaling for the DL backhaul subframe allocation. Independently, incase that each UL subframes #5, #6 and #8 (e.g., subframe indexes 6, 6and 8) are allocated as UL backhaul subframes through an explicitsignaling, the timing indication information can be included to indicatethe UL backhaul subframe to which the UL grant information transmittedthrough the DL backhaul subframe 1 (e.g., subframe index 1).

In particular, if the N in the timing indication information indicates 4(i.e., N=4), a corresponding UL grant indicates that a UL subframehaving an index set to 5 is allocated as a UL backhaul subframe. If N=7,it is able to indicate that a UL subframe having an index set to 8 isallocated as a UL backhaul subframe.

Moreover, the N value of the corresponding timing indication informationis able to indicate an interval (i.e., an index difference) between a ULsubframe index for transmitting a UL grant and a UL subframe index for acorresponding UL transmission occurrence. Alternatively, the N value ofthe corresponding timing indication information can be defined as aninterval added to a predefined reference value (e.g., a basic differencevalue between a UL grant and an uplink transmission in LTE system). Ascan be recognized from the example of the UL backhaul subframeallocation performed through the above-mentioned explicit signaling, theN value of the corresponding timing indication information is able toindicate a sequential indication value for each subframe allocated as abackhaul subframe among UL subframes next to 4 subframes, whichcorrespond to a reference value with reference to a timing point oftransmitting a UL grant in a DL backhaul subframe. In particular,according to the above example, a UL backhaul subframe #5 is indicatedas a first UL backhaul subframe, a UL backhaul subframe #5 i6 indicatedas a second UL backhaul subframe, a UL backhaul subframe #8 is indicatedas a third UL backhaul subframe. This can be indicated by the timingindication information N.

In the following description, based on a reference signal received by arelay node from a base station through a DL backhaul subframe, a methodof feeding back information on a channel status to the base station isexplained.

First of all, a relay node is able to perform an initial channelmeasurement on a DL backhaul through a DL reference signal of a basestation in an initial setting procedure. The relay not is able totransmit a result of the channel measurement in such a form as CQI, PMIand the like to the base station through a higher layer signaling. Sucha channel measurement result report made by the relay node is periodicor aperiodic. A method for a relay node to report a channel measurementresult to a base station periodically is explained as follows.

First of all, feedback information, e.g., a reference value for CQI canbe set in advance. For instance, an initial CQI value of an initialsetting of a relay node can be set as a reference value. And, a CQIreport period is divided into a long-term period and a short-termperiod. If so, the relay node reports a differential value for apreviously ser reference value in a short-term period to the basestation and is also able to report a real CQI value for updating areference value to the base station in the long-term period. Optionally,the relay node is able to feed back the differential value for thereference value periodically. And, the relay node is able to report theactual CQI value to the base station to update the reference value onlyif the differential value for the reference value exceeds a prescribedthreshold. Optionally, the relay node is able to feed back adifferential value for a last reported CQI value to the base station. Inorder to prevent error propagation, the relay not is ale to transmit aCQI feedback to the base station on a data channel. The base station isthen able to feed back a corresponding ACK/NACK to the relay node.

In the following description, a method for a relay node to report achannel measurement report to a base station aperiodically is explained.

First of all, according to an event-triggering scheme, a relay node isable to feed back CQI to a base station only if a difference between achannel measurement result and a last fed-back CQI value is equal to orgreater than a specific threshold. Each relay node is able to perform achannel measurement using such a reference signal as CRS/DRS of a DLbackhaul subframe. As a result of the channel measurement, if thedifference from a previous CQI value does not exceed a specificthreshold, the relay node is able to omit the CQI feedback to the basestation. On the contrary, if the difference from the previous CQI valueexceeds the specific threshold, the relay node is able to transmit anupdated CQI value in such a form as a message and the like to the basestation. In this case, the updated CQI value includes a real measurementvalue or a differential value from a previous CQI value.

Having relieved the updated CQI value from the relay node, the basestation is able to perform a link adaptation procedure on the relay nodebased on the updated CQI value until receiving a newly updated CQI valuein the future.

Regarding the threshold value for updating the CQI value, each time thebase station receives an updated CQI value, it informs the relay node ofa newly updated threshold value in response to the received updated CQIvalue. Alternatively, the base station informs the relay node of athreshold value in response to an initial CQI report through an initialsetting procedure of the relay not and keeps using the correspondingthreshold value. Alternatively, only if an update is necessary, the basestation is able to inform the relay node of an updated threshold value.

FIG. 3 is a diagram for one example of a frame structure used for a DLtransmission by a base station and a relay node.

Referring to FIG. 3 (a), a donor base station is able to transmitcontrol information to both a relay node and a user equipment on PDCCH(physical downlink control channel) 310. And, the base station is ableto semi-statically allocate a physical resource block (PRB) for atransmission of R-PDCCH that is a PDCCH for the relay node, which can benamed a relay zone 320. The relay node is able to receive the R-PDCCHthrough a blind search for the corresponding relay zone. In this case,the R-PDCCH is a kind of a control channel for the base station totransmit various kinds of control information to the relay node.

When the relay node feeds back a channel measurement result to the basestation, it is able to send two types of the channel measurement result.According to a first type, the relay node is able to feed back CQI/PMIfor a whole DL band in the same manner of a conventional widebandCQI/OMI feedback. On the other hand, according to a second type, therelay node is able to feed back CQI/PMI for a frequency band occupied bythe PRBs semi-statically allocated for the R-PDCCH transmission, i.e.,for a band occupied by the relay zone 320. In order for the relay nodeto perform the two kinds of the CQI/PMI feedbacks, the relay node needsto receive a signaling from the base station.

The base station is able to independently set a feedback timing and acycle for each of the two types. For instance, the base station is ableto alternately set a CQI feedback cycle of the first type and a CQIfeedback cycle of the second type. The relay node transmits the firsttype CQI feedback or the second type CQI feedback by adding a 1-bit typeindicator field, thereby enabling the base station to identify whetherthe relay node has transmitted the CQI feedback of the first type or theCQI feedback of the second type.

According to a CQU feedback method of another type, the relay node isable to make a CQI report by a subband unit. In this case, a size of acorresponding subband can be determined in consideration of a bandwidthof the relay zone 320 as well as the whole bandwidth. In particular, itis able to set a subband size to a divisor of the relay zone bandwidth.

Moreover, the relay node is able to feed back the CQI/PNI for the restof the bands except the zone (i.e., a resource occupied by the PRBallocated for the R-PDCCH transmission), which becomes a CQI feedbacktarget of the second type on the whole DL band, to the base station.

FIG. 4 is a diagram for one example of a frame structure used by a basestation in a wireless communication system using a relay node.

Referring to FIG. 4, each relay node is able to transmit UL controlinformation to a base station using an embedded control channel 410existing in a form embedded with a channel for transmitting UL backhauldata. In particular, an RN-specific (relay node-specific) controlchannel can be allocated. And, the relay nodes are able to transmit theUL backhaul data to the base station on RN-specific data channels 420,430, 440, 450 and 460, respectively.

The relay node is able to transmit a UL ACK/NACK and a schedulingrequest (RS) from the base station for the DL backhaul transmission tothe base station on a relay node control channel. Yet, the relay node isable to transmit CQI/PMI/RI feedback using a data channel. For a controlsignal transmitted on the data channel, the base station is able to feedback ACK/NACK to the relay node via PHICH (physical HARQ indicatorchannel). On the contrary, a UL control channel for a UL ACK/NACK and ascheduling request from the relay node can have a form of a commoncontrol channel of each relay node and can be allocated by FDM(frequency division multiplexing) with the data channel. The controlchannel of each relay node can have a modulation and coding scheme (MVS)different from that of the data channel.

Referring to FIG. 4, a relay node is able to transmit one ACK/NACK for awhole DL backhaul traffic via a relay node control channel. In case thatthe relay node individually transmits data to each user equipment, therelay node is able to transmit a plurality of ACK/NACK (i.e., ACK/NACKbundling) to a base station.

In case that a control channel for a relay node is not separatelyallocated, the relay node is able to transmit UL ACK/NACK to a basestation using a sounding reference signal (SRS) for a DL transmission.For this, 2 sounding reference signals can be allocated to each relaynode. In order to transmit ACK/NACK for a received DL backhaul subframe,the relay node selects a sequence corresponding to ACK or NACK in twosequences allocated via a sounding reference signal region of a ULbackhaul subframe matching the DL backhaul subframe and is then able totransmit the selected sequence to the base station.

FIG. 5 is a diagram for a configuration of a relay node apparatusaccording to a preferred embodiment of the present invention.

Referring to FIG. 5, a relay apparatus includes a receiving unit 510, achannel status measuring unit 520, a transmitting unit 530 and a memory540.

The receiving unit 510 is able to receive various kinds of controlinformation and data from a base station and is also able to receivesignals, data and the like from a user equipment. The receiving unit 51is able to receive a DL backhaul subframe containing UL grantinformation from the base station. The transmitting unit 530 is able totransmit a UL signal via a corresponding UL backhaul subframe based onthe DL backhaul subframe received by the receiving unit 510, UL backhaulsubframe configuration information and the like.

The channel status measuring unit 530 is able to measure a channelstatus using a DL reference signal of the base station received by thereceiving unit 510. The transmitting unit 530 combines or generates themeasured channel status value into various forms and is then able totransmit it to the base station. For instance, the transmitting unit 530transmits a differential value between the measured channel status valueand a reference value to the base station. If the differential value isgreater than a preset threshold value, the transmitting unit 530transmits the measured channel status value to the base station or isable to transmit a differential value between the measured channelstatus value and a last reported channel status value to the basestation.

The memory 540 is able to store information processed by the relayapparatus for a prescribed period of time and can be replaced by such acomponent as a buffer (not shown in the drawing) and the like.

As mentioned in the foregoing description, the detailed descriptions forthe preferred embodiments of the present invention are provided to beimplemented by those skilled in the art. While the present invention hasbeen described and illustrated herein with reference to the preferredembodiments thereof, it will be apparent to those skilled in the artthat various modifications and variations can be made therein withoutdeparting from the spirit and scope of the invention. Thus, it isintended that the present invention covers the modifications andvariations of this invention that come within the scope of the appendedclaims and their equivalents. For instance, the respectiveconfigurations disclosed in the aforesaid embodiments of the presentinvention can be used by those skilled in the art in a manner of beingcombined with one another.

Therefore, the present invention is non-limited by the embodimentsdisclosed herein but intends to give a broadest scope matching theprinciples and new features disclosed herein.

INDUSTRIAL APPLICABILITY

Accordingly, an uplink signal transmitting method of a relay apparatusand a feedback information transmitting method thereof according to thepresent invention is applicable to various wireless communicationsystems such as 3GPP LTE system and the like.

1. A method of transmitting an uplink signal at a relay node (RN) in awireless communication system, the method comprising: receiving adownlink (DL) backhaul subframe including a UL grant information from abase station (BS); and transmitting a signal to the base station (BS)via a specific uplink (UL) backhaul subframe based on the received ULgrant information, wherein the UL grant information includes a timingindication information and wherein the timing indication informationcomprises information about an interval from a DL backhaul subframecorresponding to the received UL grant information to the UL backhaulsubframe transmittable in UL by the relay node.
 2. The method of claim1, wherein the interval is a subframe unit.
 3. The method of claim 2,wherein the interval corresponds to one of 4 subframes, 5 subframes and6 subframes.
 4. The method of claim 1, wherein the interval isdetermined in consideration of a processing time of the RN and afeedback timing of an ACK/NACK (acknowledgement/non-acknowledgement)signal for the DL backhaul transmission.
 5. A method of transmitting anuplink signal at a relay node (RN), the method comprising: receiving adownlink (DL) backhaul subframe pattern information from a base station(BS); and transmitting the uplink signal to the base station via auplink (UL) backhaul subframe based on an interval informationindicating interval from the DL backhaul subframe to the UL backhaulsubframe, wherein the DL backhaul subframe pattern information includesindex information of the DL backhaul subframe and wherein the intervalinformation is a predetermined value or is signaled from the basestation.
 6. A method of transmitting feedback information at a relaynode (RN) in a wireless communication system, the method comprising:receiving a downlink (DL) reference signal from a base station (BS);measuring a channel status using the received DL reference signal; andtransmitting a differential value between the measured channel statusvalue and a reference value, the measured channel status value when thedifferential value is grater than a preset threshold value) or adifferential value between the measured channel status value and a lastreported channel status value to the base station as the feedbackinformation.
 7. The method of claim 6, wherein the reference value isset to an initial channel status value during an initial setup of therelay node.
 8. A method of transmitting feedback information at a relaynode (RN) in a wireless communication system, the method comprising:receiving a downlink (DL) reference signal from a base station;measuring a channel status using the received DL reference signal; andtransmitting the measured channel status value or the differential valueas the feedback information to the base station when a differentialvalue between the measured channel status value and a last reportedchannel status value is equal to or greater than a preset thresholdvalue.
 9. The method of claim 8, further comprising: receiving anupdated threshold from the base station in response to the feedbackinformation transmission.
 10. The method of claim 8, wherein themeasured channel status value is a first type channel status value for awhole downlink (DL) band or second type channel status value for aspecific frequency band occupied by a physical resource block (PRB)allocated for a PDCCH (physical downlink control channel) transmissionfor the relay node.
 11. The method of claim 10, wherein the feedbackinformation includes information indicating whether the measured channelstatus value is the first type channel status value or the second typechannel status value.
 12. The method of claim 8, wherein the measuredchannel status value is a value of a subband unit.
 13. The method ofclaim 8, wherein the measured channel status value is transmitted to thebase station via a data channel.
 14. A relay node (RN) apparatus fortransmitting an uplink signal in a wireless communication system, the RNapparatus comprising: a receiving unit for receiving a downlink (DL)backhaul subframe including a UL grant information from a base station(BS); and a transmitting unit for transmitting a signal to the basestation via a specific uplink (UL) backhaul subframe based on thereceived UL grant information, wherein the UL grant information includestiming indication information and wherein the timing indicationinformation comprises an information about an interval from a DLbackhaul subframe corresponding to the received UL grant information tothe UL backhaul subframe transmittable in UL by the relay node.
 15. Arelay node (RN) apparatus for transmitting feedback information in awireless communication system, the RN apparatus comprising: a receivingunit for receiving a DL reference signal from a base station; a channelstatus measuring unit for measuring a channel status using the receivedDL reference signal; and a transmitting unit for transmitting adifferential value between the measured channel status value and areference value, the measured channel status value when the differentialvalue is grater than a preset threshold value or a differential valuebetween the measured channel status value and a last reported channelstatus value to the base station as the feedback information.
 16. Themethod of claim 6, wherein the measured channel status value is a firsttype channel status value for a whole downlink (DL) band or second typechannel status value for a specific frequency band occupied by aphysical resource block (PRB) allocated for a PDCCH (physical downlinkcontrol channel) transmission for the relay node.
 17. The method ofclaim 6, wherein the measured channel status value is a value of asubband unit.
 18. The method of claim 6, wherein the measured channelstatus value is transmitted to the base station via a data channel.